Boring method

ABSTRACT

A horizontal boring method comprises the steps of boring a small diameter pilot hole, thereafter removing the small diameter bit, then boring the final diameter of the bore hole by advancing a boring bit having a lead-off bar guided within and by said pilot hole, simultaneously advancing a cylindrical casing immediately behind said bit, introducing a liquid into the end of the casing to slurry the cuttings and finally, when the boring step is completed, removing the bit through the casing and cleaning the thus installed casing. A roller bit is provided which is comprised of a pilot bit mounted on a lead-off bar which is attached to the final boring bit having roller overcutters which are retractable to permit removal of the assembly back through the casing when the casing has been completely installed. The method and apparatus has particular utility in horizontal boring such as when installing drain pipe, utility mains, etc., under pre-exisiting paved areas and the like.

United States Patent 1191 Dunn Sept. 2, 1975 BORING METHOD [75]Inventor: Richard P. Dunn, Wichita Falls, Primary Examiner-Deva Br ownTex. Attorney, Agent, or Fzrm-Gardmer, S1xbey, Bradford and Carlson [73]Assignees International Boring Systems Co.,

Wichita Falls, Tex.

22 Filed: May 23, 1974 ABSTRACT [21] Appl. No.: 472,673 A horizontalboring method comprises the steps of boring a small diameter pilot holethereafter remov- A D Z Related U S pphcatmn am mg the small diameterbit, then boring the final diame- [62] 2 July 1973 ter of the bore holeby advancing a boring bit having a lead-off bar guided within and bysaid pilot hole, simultaneously advancing a cylindrical casing immedi-[g2] l75]/E6221,B1Zg;(5)g ately behind said bit, introducing a liquidinto the end [58] Fl .ld 162 171 of the casing to slurry the cuttingsand finally, when 1 le 0 earc 1715/1 the boring step is completed,removing the bit through the casing and cleaning the thus installedcasing.

[56] References Cited roller bit is provided which is comprised of apilot UNITED STATES PATENTS bit mounted on a lead-off bar Wl'llCh isattached to the final boring bit having roller overcutters which are1932968 10/1933 Enlglebnght et retractable to permit removal of theassembly back 52:2 /53 through the casing when the casing has been 3:011:567 12/1961 Turner 175 53 completely mstaned' 3,190,376 6/1965Christensen 175/62 X The method and apparatus has particular utility in3,232,360 2/1966 Dickinson 175/62 horizgntal boring uch as wheninstalling drain pipe, 3,402,781 9/ 1968 safldberg 175/62 X utilitymains, etc., under preexisiting paved areas and 3,656,563 4/1972 Blmnel75/62 X the like 3,805,899 4/1974 Hicks et al. 175/62 X POWER ANDADVANCE UN IT Austria 175/53 1 Claim, 4 Drawing Figures PAVEMENTCOMPACTED SUB-SURFACE NATURAL STRATE' PILOT HOLE 5 PATENTE'U SEP 21975sum 1 0f 3 \m 50: SE 8 Q. m A 525 i252 PATENTEUSEP PATENTED 21535 3 902563 sum 3 of 3 BORING METHOD This is a division of application Ser. No.380,409, filed 7/18/73, now US. Pat. No. 3,837,413.

BACKGROUND The boring of the earth is an ancient and well-known processinvolving the use of a variety of boring bits, power sources, bore holelinings and the like for any number of purposes. The bore holes may varyin size from less than an inch to as large as or feet depending on itspurpose. Boring is done vertically, horizontally and at almost everyimaginable angle, again as a consequence of the function which the borehole will serve.

Regardless of the function of the finished bore hole, there aredifficulties that plague such operations in respect of accuracy indetermining that the boring operation results in a bore hole which issuitable for its intended purpose both in direction and line. The latterrequirement is particularly important where the bore hole is to be linedwith a casing such as steel or plastic pipe or the like. The formerrequirement is particularly important where the bore hole is madethrough or adjacent existing environment or objects which cannot bedisturbed. The difficulties in controlling line and direction are lesscritical where the bore hole is vertical but become more and moremagnified as the direction of the bore hole approaches the horizontaland gravitational and deflective forces come into play.

By way of example of a typical situation to which the inventionpertains, let it be assumed that after completion of a dual lane highwayincluding a median strip formed as a drainage swale of lower elevationbetween the ribbons of pavement area, it is discovered that for onereason or another drainage of the median strip is necessary. To effectsuch drainage a drain pipe or culvert must be installed beneath thepavement and underlying roadbed.

The installation of such a drain pipe or culvert can be effected inseveral ways. The first mode is by digging up the highway and underlyingsubsurface to the required level and, after installing the conduit,refilling the area and repaving the disrupted pavement. This operationis fraught with disadvantages in that the paved area must be closed totraffic; it is time consuming; it is difficult to refill the dug up areaand obtain the desired degree of subsurface compaction as is required tosupport the pavement; it is virtually impossible to repair the pavementarea with any degree of certitude that the repaved area will bepermanent and not subject to rapid deterioration and finally, this modeis very expensive.

The second mode of conduit or culvert installation is by a boring methodwhich has been an adaptation of vertical drilling, as for drilling wellsand the like, to horizontal drilling. In this operation, a hole is boredhorizontally following the desired direction, elevation and, hopefullyline, so that the bore hole will not disrupt either the pavement or thesubsurface therefor. After drilling or in many cases, concurrently withdrilling, the bore hole is lined with a casing, usually steel or plasticconduit of the desired size which may be, in some cases, grouted inplace in the bore hole. The liner or casing assures against collapse ofthe bore hole after drilling and during its useful life.

The second mode of operation, while a more desirable operation than thefirst mode described is not,

however, without disadvantages. For, in drilling a horizontal bore hole,it is very difficult to control the line and direction of the drillingdue to such factors as varying soil conditions, deflection of the drillbit due to its own weight and torque loads generated in the bit rotatingand advancing machinery. Because of these factors, many times a borehole will simply not follow a straight line or will not exit at theproper location despite careful efforts to control its line anddirection by every known surveying and measuring method. When such abore hole goes awry it is necessary, not only to repeat the drillingoperation, but the faulty bore hole must be refilled in a methodacceptable to the particular requirements of the jurisdiction in whichthe work is being done. Obviously, too, the expense and time consumed inrefilling and reboring is of great concern to the entity performing thework.

In the most widely used horizontal boring operations the generalpractices fall into the dry" boring category, i.e. the cuttings are fedback through the bore hole toward the entrance end as broken up dry,that is without varying its moisture content, material. Where the stratato be bored is soil, i.e., clay, sand, etc., absent rock content, aconventional dirt toothed bit is used. Where the strata to be bored isrock formation, carbide teeth are substituted for the conventional dirtteeth.

In methods employing the simultaneous installation of easing, the twomajor boring methods involve the use of either (a) non-removable cuttingheads, or (b) re movable cutting heads. The former type of cutting headis sized to the approximate diameter of the casing which is forced inthe bore hole behind it and therefore cannot be removed from the borehole until itemerges at the exit side. Thus, if the head jams or teethbreak during the boring operation, the problem is virtuallyinsurmountable. The mentioned type of cutting head is provided withvariable diameter side cutters which expand out, when the head isrotated in the boring direction, to the casing size and retract, whenthe head is rotated in the opposite direction, so that the head may beremoved through the casing. While this type of head obviates the jammingand breakage problem, it does so at the expense of ,very high powerrequirements and very high torque loading of the driving and advancingapparatus due to the very high power demands of side cutting blades. Byway of further information as regards the above-noted cutting heads,reference may be had to drill heads manufactured and sold by CRC-CROSEInternational Inc. of Houston, Tex.

THE PRESENT INVENTION The present invention, in large measure, seeks toresolve many, if not all of the prior art modes of boring horizontalbore holes and easing same. Accordingly, a first object of the inventionis to provide a method of boring which virtually eliminates misdirectionof the bore hole and casing.

Another object of the present invention is to provide a method ofhorizontal boring in which the casing is installed simultaneously withthe boring operation.

Still a further object of the invention is to provide a method ofboring, wherein the difficulties and errors inherent in prior artmethods are obviated or virtually eliminated.

An additional object of the invention is to provide a novel bitstructure particularly adapted for use in horizontal boring operations.

The specifically mentioned objects are but a few of the objectives ofthe invention which are inherent therein as will be obvious to thoseskilled in the art from the detailed description which follows. In thedescriptive material reference is made to the drawing forming a parthereof and wherein:

FIG. 1 is a schematic view showing the first step in the process,

FIG. 2 is a schematic view showing the second operation involving anumber of process steps,

FIG. 3 is side view of a drilling head particularly useful in performingthe method of this invention while,

FIG. 4 is an end view of the head disclosed in FIG.

Considering FIG. 1, it may be seen that a situation typifying theexample given in the background, there is a pavement area of concrete,asphalt or the like, resting on the compacted subsurface which in turnrests on the natrual strata be it simply rock-free soil, or rockyformations or combinations thereof. As shown, the pavement surface iselevated above the swale 40 which must be drained or whatever bycommunication with the low area to the right-hand side of the drawing.

In order to avoid disturbance of the pavement and compacted subsurfacewith all of the previously noted disadvantages, the novel method of thisinvention is employed to install a drainage conduit or culvert. As shownin FIG. 1, the area of the swale immediately adjacent the roadbed may beexcavated as required to permit positioning of a portable power anddrill advance unit 1 to be lowered to the elevation at which the boringoperation is to take place. In cases where the elevation of the swale islow enough the excavation can be dispensed with as should be obvious.The power and advance unit, which forms no part of this invention, in-

cludes a prime mover, a torque output means for driving the rotary drillshaft and a reciprocating carriage having means to advance both pipe andcasing into the bore hole. A typical example of such a unit is shown inthe co-pending application of Richard P. Dunn, Ser. No. D278,349, filedAug. 7, 1972.

Once in position at the proper elevation and after a proper survey orcalculation for line and direction, the power unit has attached thereto,in the conventional manner, a small diameter drill bit 3, driven byshaft 7, on the order of two to four inches, is rotated and advancedalong the calculated direction to bore a pilot hole 5 underneath theroadbed. The pilot hole 5 extends completely through the natural stratato the exit point of the proposed culvert and the exit point is closelychecked by suitable measurement to determine that its exit is in theproper location. When it has been determined that the exit of the pilothole is satisfactory, the pilot bit and its drive shafting are removedfrom the pilot hole.

With the final boring to be undertaken, the power and advance unit isprovided with a boring head 50 attached to suitable shafting 7 and isrotated and advanced to commence the final boring. The boring head 50 isprovided with a pilot bit 9 of substantially the same size as the pilothole mounted on a lead-off bar 11, and is followed by an auger 13mounted for simultaneous rotation with the boring head 50."

The pilot bit 9 is inserted in the previously drilled pilot hole 5 whichacts to guide the pilot bit along the same line and direction as theacceptable pilot hole to assure that the bore hole 17 also follows thesame line and direction and exits at the proper predetermined location.

The boring head 50 is provided with face cutters and, as wellovercutters, as will be described in detail, whereby the diameter ofbore hole 17 is large enough to slidably accept the tubule conduit orcasing 19 which is advanced by the power and advance unit 1 behind theboring head 50. The size of the bore hole 17 relative to the casing(shown exaggerated in FIG. 2) is also large enough to permit insertionof a liquid-carrying pipe 21 disposed between the casing 19 and theinterior of the bore hole 17. The discharge end of the pipe is fixed byany suitable means to the advancing end of the casing and has itsdischarge end directed inwardly toward the center of the bore hole 17and is advanced along with the end of the casing into the progressingbore hole 17.

Immediately behind boring head 50 and carried by the power-drivenshafting 7 is the auger 13 which fits inside casing 19 and serves totransmit cuttings rearwardly toward the entrance end of the casing,i.e., toward the power unit 1. Preferably, the area of operations ofboring head 50 is flooded with water from the pipe 21 so that thecuttings are reduced to more or less slurry form to be easily moved byauger 13 and discharged from the interior of the advancing casing 19.

Since the pilot bit follows the pilot hole, it being the path of leastresistance, successful boring to the proper exit location is virtuallyassured.

Once complete, the boring head 50 can, along with pilot bit 9, lead bar11 and auger 13 be readily removed from the casing in either direction,the casing flushed clean and the operation is complete. In someinstances, the process may involve the insertion of grouting between theinterior of bore hole 17 and casing 19 but this step is a function ofstrata conditions and may not be necessary though it is an optionalstep. Finally, the power unit is removed and the excavation, if there bean excavation, is closed in the conventional manner.

After removal of the boring head, the conduit or culvert may be easilycleaned out by washing same with water from a hose or the like having inmind that the bulk of the cuttings have previously virtually all beencleaned out of the casing in slurry form during the boring operation.

It can thus be seen that the practice of the method results in aconsiderable reduction in numbers of bad holes bored, since the use ofthe pilot hole which is relatively inexpensively and quickly bored,assures proper line and direction of the final boring by obviating thetendency of the boring head 50 to deviate from its chosen path due toany one or all of the factors outlined in the discussion previoushereto.

It might be stated, here, that the manner of adding and removing shaftlengths and casing sections between the power and advance unit and theadvancing head 50 is quite well known in the art and need not be laboredsince reference may be had to U.S. Pats. Nos. l,4l3,47l; 2,234,45l;2,588,068 and 3,0l 1,567, for such teachings. The addition of casingsections to form the desired length of casing as it is advanced followspractices quite similar to conventional practices in well drilling andneed not be described in great detail.

It should be further noted that the present method may result in thedeletion of the behind-head auger l3 where strata conditions so permit.In such cases, the strata cuttings slurry quite readily and simply flowback into the advancing casing and are subsequently flushed out when theboring operation and casing installation are complete.

In some cases, however, the use of the auger is believed necessary aswhere for example, the strata does not slurry readily or is rock. Theaddition ,of water, however, does facilitate the operation since it willflush smaller cuttings back and also serves to lubricate the cutting andauger flights to reduce friction as the cuttings are moved rearwardlyand thus reduce power requirements. I

Turning now to FIGS. 3 and 4 a novel boring head 50 for use in thedescribed method is shown in detail. It should be understood, however,that the described boring head can be used in a dry boring or reamingoperation and, thus, is adapted for broad utility.

The head 50 includes a rod-like head shaft51 having a working end and acoupling end 52 or left and righthand end as shown in, FIG. 3. Thecoupling end 52 fits with the end of torque shaft 7 shown in dotted lineoutline and is fastened therein by bolt and nut assemblies 53, thelatter also shown in dotted line outline, since various other couplingmeans can be used. The coupling of head shaft 51 to the driven shaft 9is affected just inwardly of the advancing end of casing 19 regardlessof what coupling means is used.

The head shaft 51 extends a substantial distance, beyond its place ofcoupling with the driven shaft 52 and terminates in its working end inan internal threaded socket 54. Threaded into the socket is a lead-offbar 11 which in turn terminates in socketed end 55. Threadedly connectedin the socketed end of lead-off bar 11 is a removable pilot bitconsisting of a plurality of forwardly extending trunnions 57 havingjournalled therein a plurality of toothed cutting cones 59. The axis ofrotation of the toothed cones 59 is so disposed that the rotatingsurface of the toothed cones forms a line contact with an imaginaryvertical surface extending across the face of the pilot hole bit.

The diameter of the pilot hole bit 9, i.e. the working face thereof,will vary depending on the size of the pilot hole previously drilledwhich, in turn, is a function of the final diameter of the bore hole tobe bored to finished dimensions by the boring head 50. Generallyspeaking, the larger the bore hole, the larger is the pilot hole.

Similarly, the length of lead-off bar 11 may vary in accordance withboring head and pilot bit size and the type of strata into which thebore hole is being advanced. There is no empirical formula or fixedrelationship which can be used to determine the length of the lead-offbar 1]. Selection of a length is a matter of experience and judgment asapplied to existing conditions.

Interposed between the lead-off bar socket 54 in head shaft 51 andcoupling socket 52, the head shaft carries a cutter support 61 in theform of an annular plate securely fixed thereto as by welding or thelike. Projecting outwardly from the support 61 toward the pilot bit andat angularly spaced intervals are a plurality of trunnions 63 which inturn carry rotatable toothed cutter cones 65. Cutter cones 65 are of asignificantly larger size than the smaller cones 59 and also are sodisposed about inwardly and downwardly inclined axes so that the conesurfaces would define line contact with an imaginary vertical surface.The cones 65 define in part the principal cutting means for the boringhead in forming the bore hole 17.

' Immediately behind the support plate 61 there are provided a pluralityof journals 67, disposed at equal angular spacing around the surface ofthe shaft 51 and welded thereto with their respective centers alignedalong an axis disposed parallel to the axis of shaft 51. Within thejournals 67 are fitted a plurality of pivot pins 62 which carry a pairof spaced hinge pintles 69, 71. Pintles 69 and 71 are welded to thelower ends of pairs of pivot arms 73, 75 which with tie plate 77 definea swingable yoke. The forward, that is cutter end of the tie plate 77and pivot arm 73, have attached thereto forwardly projecting overcutterjournals 79 in which are journalled further toothed cone shaped cutters81. Cutters 81 are rotatable about axes disposed down wardly andinwardly toward the central axis of the cutter head'so that their outersurface, i.e. the toothed cone surface, would establish line contactwith an imaginary vertical plane passing transversely through and atright angles to the shaft 51. The cutting cones 81 define with cones 65the boring means for establishing the metes and bounds of bore holes 17.

As is obvious, the cutter cones 81 are thus so mounted asto be swingableabout the axis of pins 62 and means must be provided to retain thesecones in effective cutting position, yet permit of swinging as and forthe purposes to be set forth. To this end, a solid generally rectangularplate member 83 is affixed, as by welding or the like, betwen pivot arms73 and 75. The plate member which is a movable stop means is sopositioned as to rest against a second plate 85, defining a fixed stopmeans, which is affixed to the head shaft 7 and is in the form of a flatrectangular plate disposed diametrically of shaft 7 medially of thepintles 69 and 71, and has its inner edge welded to the shaft andjournal 67. It is to be noted that plate 85 extends outwardly from thejournal 61 such that the movable stops means 83 lies on one side of itsplanar surface while the axis about which the pivot arms 73 and 75 swinglies on the opposite side thereof. Thus, the pivot arms can only swingoutwardly as far as stop means 83, 85 permit, but they can swing in theopposite direction, i.e., inwardly toward head shaft 51 for somedistance until they abut against the shaft. Thus the cutters 81 can beopened to circumscribe an area defined by the wall of bore hole 17larger than the diameter of casing 19 when the head shaft is rotated inthe working direction, i.e., counterclockwise as shown in FIG. 4.However, when the head shaft is rotated in the reverse direction, thepivot arms swing inwardly through are A and hence the cutter cones 81are drawn in and circumscribe an area which is less than the areacircumscribed by casing 17 and hence the cutter head can be withdrawnback through the casing 17.

The novel boring head structure, then, provides for removal of the headback through the casing in the event of jamming or breakage. At the sametime, since it is a roller boring head, it provides all the advantagesof roller bits, such as smooth operation and low power requirements, tomention but a few of such advantages.

After the bore hole is completed the whole assembly, auger 13, head 50and shaft 7 may be readily removed by withdrawal back through the casedculvert or drain or the boring head 50 may be removed from torque shaft7 at its connector end 52 leaving only the auger 13 and shaft 7 to bebroken down and removed from the power unit side of the culvert.

Finally, where soil conditions so demand, the small area around thecasing 19 between it and the bore hole 17 may be filled with a groutingmaterial. In most cases, natural settlement causes the bore hole tocollapse against the casing 19 making a grouting operation unnecessary.

Having described the invention in detail, it will be apparent thatvarious modifications will occur to those skilled in the art and whichfall within the purview of the novel subject matter as defined in theclaims, wherein:

What is claimed is:

l. A method of installing generally horizontal cased bore holes such asdrainage culverts, electrical conduit passages and the like, comprisingthe steps of a. positioning a power source at a grade level at which thehole. is to be bored and the casing installed;

b. establighing the line and grade for the hole to be bored and cased;

drilling a small diameter pilot hole along said determined line andgrade;

d. boring the final diameter hole with a boring head having a diameterslightly larger than the diameter of the casing to be installed in saidbore hole, and further, having a pilot hole bit which follows in thepreviously bored pilot hole;

. advancing a casing of slightly less diameter than g. discharging aliquid from said outlet inwardly toward the center of said casingwhereby the cuttings from said boring head are slurried behind theboring head and readily carried through the advancing casing toward saidpower source for discharge from the casing.

1. A method of installing generally horizontal cased bore holes such asdrainage culverts, electrical conduit passages and the like, comprisingthe steps of a. positioning a power source at a grade level at which thehole is to be bored and the casing installed; b. establighing the lineand grade for the hole to be bored and cased; c. drilling a smalldiameter pilot hole along said determined line and grade; d. boring thefinal diameter hole with a boring head having a diameter slightly largerthan the diameter of the casing to be installed in said bore hole, andfurther, having a pilot hole bit which follows in the previously boredpilot hole; e. advancing a casing of slightly less diameter than thefinal bore hole diameter into said bore hole immediately behind saidfinal boring head; f. simultaneously advancing with the casing,Externally thereof a liquid carrying conduit having a discharge outletpositioned immediately behind the boring head but beyond the end of thecasing; g. discharging a liquid from said outlet inwardly toward thecenter of said casing whereby the cuttings from said boring head areslurried behind the boring head and readily carried through theadvancing casing toward said power source for discharge from the casing.